1. Field of the Invention
The present invention relates to wildlife guards for protecting electrical equipment from shorts caused by wildlife, and in particular, to such a wildlife guard that is easily aligned and installed on an insulator bushing.
2. Brief Description of the Related Art
Squirrels, birds, and the like often climb onto or perch on transformers, power lines, and insulator bushings. If the distance between an energized terminal and a ground or another terminal is too short, an animal may come into contact with both at the same time. This will typically cause an electrical short and kill the animal. It may also damage equipment and cause power outages. Wildlife guards are typically used as a barrier to maintain adequate space between the animal and the energized part to decrease the chances of an animal causing an electrical short.
U.S. Pat. No. 4,845,307 issued to Cumming et al. discloses a one-piece guard with a V-shaped indentation running down one side. A cut is made in the bottom of the V-shaped indentation, forming a slot. To install the guard, a worker using a live-line tool, pushes or pulls the V-shaped indentation against a cable so that the cable pops through the slot into the interior of the guard. Inner protrusions snap into place over the uppermost skirt of the bushing.
U.S. Pat. No. 6,005,196 to Spillyards discloses a guard having two hinged body sections that are biased by a spring assembly toward a closed position. Before installation, a releasable trigger keeps the guard in an open position until the trigger is released. To install the guard of Spillyards, a worker using a manipulator pole pushes the guard over a power line. The power line trips the releasable trigger, and the two body sections snap shut around the line. The installer then pulls the guard down over the topmost skirt of the bushing.
U.S. Pat. No. 6,255,597 to Bowling et al. discloses a guard having two cover portions that are pivotally connected, but the two cover portions are not spring-biased toward a closed position. Instead, the guard of Bowling et al. relies upon force applied to lever arms as the guard is pushed against a bushing to move the guard to a closed position. To install the guard of Bowling et al., a worker using a manipulator pole forces the lever arms against a bushing, and that force moves the cover portions to a closed position.
All three of these guards are very difficult to install in close proximity to the electrical equipment and extremely difficult to install from the ground.
U.S. Pat. No. 5,648,641 to Guthrie discloses a guard that takes a very different approach to the problem of providing a barrier to animals and relies on current passing through the live wire to create an electrostatic charge in a plurality of radially-extending spokes. Guthrie discloses an embodiment in which a gap is left between the ends of two semi-circular sections opposite a spring. The gap facilitates installing the device onto a bushing.
U.S. Pat. No. 3,042,736 to G. F. Salisbury discloses a protective cover to protect linemen by enclosing wire, insulators, switches, etc. with insulating protective covers. The cover is a corrugated sleeve with enlarged annular flanges of resilient material lying in planes transverse to the axis of the sleeve. Slots are formed in the sleeve and the flanges. The resilient flanges tend to bias the edges of the slots together. Longitudinal lips have diverging ends so they define a converging entrance. The cover also has a flange or lifting bar with holes to facilitate grasping by a hot stick applicator. When the cover is forced over a power line the lips and the edges of the slots momentarily separate. After the entrance of the wire, the resilience of the material causes the edges to return to initial position. The device may then be moved along a line, until it encloses an electrical device, such as dead end bells.
U.S. Pat. No. 1,598,155, issued in 1926 to M. B. Salisbury, discloses an insulated protective cover that is pushed over both an insulator and conductors. A hood section is sized to conform to the shape of the insulator and has openings in the lower ends of its sides that are adapted to receive the conductor. At the lower end of the inner surface is a bead that secures the cover to the insulator.
U.S. Pat. No. 6,255,597 to Bowling et al. and U.S. Pat. No. 6,291,774 to Williams discloses the use of flexible fingers on a wildlife guard to allow the entry of a conductor while fitting closely around the conductor.
U.S. Pat. No. 3,824,676 to Ebert discloses a bushing cover that is positioned on a bushing using an applicator tool. The cover is a resilient sleeve having edges that normally overlap. The bushing cover may be spread open so that the edges are separated. The applicator tool has hooked channels for holding the edges apart. The cover is positioned around the bushing. As the operator pushes the cover against the bushing, the cover deforms and the edges are pulled out of the channels so that the edges snap out of the channels and closes around the bushing 16. The applicator tool has an adjustable ratchet fitting designed to fit a universal pole which has a matching ratchet fitting.
U.S. Pat. No. 4,159,395 to Cogelia discloses a self-locking cable guard having an inverted-V cross section with the legs of the V bend inwardly to define a substantially enclosed cavity for receiving the cable. The bent leg sections define an expandable resilient spaced gap which facilitates snap-on installation of the guard.
The BG-9 Wildlife Guard manufactured by Hendrix Wire & Cable, Inc., Milford N.H. is a wildlife guard for installation on the bushings of transformers and other power equipment. The guard is intended to mount over the top skirt of the bushing and is provided with a vertical internal block to ensure proper installation on a bushing. The vertical internal block does not allow for opened guards to be nested together for maximum efficiency in packing a number of guards for shipping.
References mentioned in this background section are not admitted to be prior art with respect to the present invention.